There are also several instances of "ring species." These happen when there's an obstacle to a species' spread that individuals can't cross, but can go around. Said obstacle being quite large, as compared to the distance individuals travel. So they spread around it in both directions, over multiple generations, with slight genetic drift... and when they finally meet again on the far side of the obstacle, the new neighbors can't interbreed. So variety A can cross with variety B, who can mate with variety C, and so on... but A and P, who are next-door neighbors, can't.
(Another puzzle of "where and how do you draw a species line?". Along with the notion that each individual is the same species as their own mother, but if you go some number of generations back then maybe they aren't the same species....)
There are some specimens from north-central Asia that carry the DNA of H.Sapiens Sapiens, H.Sapiens Neanderthalensis, H.Sapiens Denisova, and... um... those other H.Sapiens. Not Heidelbergensis. The ones we know absolutely nothing about except these odd traces of DNA in these specific specimens.